<template>
 <div class="s-canvas">
  <canvas id="s-canvas" :width="contentWidth" :height="contentHeight"></canvas>
 </div>
</template>
<script>
export default{
 name: 'SIdentify',
 props: {
  identifyCode: { // 默认注册码
   type: String,
   default: '1234'
  },
  fontSizeMin: { // 字体最小值
   type: Number,
   default: 25
  },
  fontSizeMax: { // 字体最大值
   type: Number,
   default: 35
  },
  backgroundColorMin: { // 验证码图片背景色最小值
   type: Number,
   default: 200
  },
  backgroundColorMax: { // 验证码图片背景色最大值
   type: Number,
   default: 220
  },
  dotColorMin: { // 背景干扰点最小值
   type: Number,
   default: 60
  },
  dotColorMax: { // 背景干扰点最大值
   type: Number,
   default: 120
  },
  contentWidth: { // 容器宽度
   type: Number,
   default: 90
  },
  contentHeight: { // 容器高度
   type: Number,
   default: 38
  }
 },
 methods: {
  // 生成一个随机数
  randomNum (min, max) {
   return Math.floor(Math.random() * (max - min) + min)
  },
  
  // 生成一个随机的颜色
  randomColor (min, max) {
   let r = this.randomNum(min, max)
   let g = this.randomNum(min, max)
   let b = this.randomNum(min, max)
   return 'rgb(' + r + ',' + g + ',' + b + ')'
  },
  
  drawPic () {
   let canvas = document.getElementById('s-canvas')
   let ctx = canvas.getContext('2d')
   ctx.textBaseline = 'bottom'
   // 绘制背景
   ctx.fillStyle = '#e6ecfd'
   ctx.fillRect(0, 0, this.contentWidth, this.contentHeight)
   // 绘制文字
   for (let i = 0; i < this.identifyCode.length; i++) {
    this.drawText(ctx, this.identifyCode[i], i)
   }
   this.drawLine(ctx)
   this.drawDot(ctx)
  },
  
  drawText (ctx, txt, i) {
   ctx.fillStyle = this.randomColor(50, 160) // 随机生成字体颜色
   ctx.font = this.randomNum(this.fontSizeMin, this.fontSizeMax) + 'px SimHei' // 随机生成字体大小
   let x = (i + 1) * (this.contentWidth / (this.identifyCode.length + 1))
   let y = this.randomNum(this.fontSizeMax, this.contentHeight - 5)
   var deg = this.randomNum(-30, 30)
   // 修改坐标原点和旋转角度
   ctx.translate(x, y)
   ctx.rotate(deg * Math.PI / 180)
   ctx.fillText(txt, 0, 0)
   // 恢复坐标原点和旋转角度
   ctx.rotate(-deg * Math.PI / 180)
   ctx.translate(-x, -y)
  },
  
  drawLine (ctx) {
   // 绘制干扰线
   for (let i = 0; i < 4; i++) {
    ctx.strokeStyle = this.randomColor(100, 200)
    ctx.beginPath()
    ctx.moveTo(this.randomNum(0, this.contentWidth), this.randomNum(0, this.contentHeight))
    ctx.lineTo(this.randomNum(0, this.contentWidth), this.randomNum(0, this.contentHeight))
    ctx.stroke()
   }
  },
  
  drawDot (ctx) {
   // 绘制干扰点
   for (let i = 0; i < 30; i++) {
    ctx.fillStyle = this.randomColor(0, 255)
    ctx.beginPath()
    ctx.arc(this.randomNum(0, this.contentWidth), this.randomNum(0, this.contentHeight), 1, 0, 2 * Math.PI)
    ctx.fill()
   }
  }
 },
 watch: {
  identifyCode () {
   this.drawPic()
  }
 },
 mounted () {
  this.drawPic()
 }
}
</script>